A conventional rotating electrical machine has rotor windings accommodated in a plurality of slots provided in a rotor iron core, each rotor winding having winding conductors obtained by stacking plate-like conductors at plural stages via insulating materials, and a plurality of through-holes formed in the plurality of conductors and the plurality of insulating materials, to form a plurality of ventilation passages through which cooling gas flows in a radial direction of the rotor iron core and flows in an axial direction of the rotor iron core. The plurality of through-holes are formed in plural lines arranged in a width direction of the conductors. In the case where the width dimension of the conductors is denoted by WC, and a sum of width dimensions, in the width direction of the conductors, of the through-holes or the ventilation passages formed in the plural lines is denoted by WH, a ventilation area of the through-holes or the ventilation passages formed in the plural lines is set so as to satisfy a relationship of 0.2≦WH/WC≦0.7 (for example, see Patent Document 1).